This invention relates to the sampling of liquid which is being delivered along a flow path. The invention is applicable to a variety of circumstances and liquids, especially viscous liquids. Hydrocarbon mixtures such as bunker fuel, lubricating oil or crude oil are notable applications. The use of the invention which is particularly envisaged is in sampling heavy fuel oil which is being supplied to a ship as bunker fuel for the ship's engine(s).
Heavy fuel oil is a very viscous material, and because of this it is customarily supplied through heated hoses at a temperature of 55.degree. C. and a pressure of about 8 bar.
With rising crude oil prices the quality of heavy fuel oil has rapidly deteriorated. An inadequate quality of fuel oil can lead to excessive engine wear and/or breakdown. For instance an excessive content of high boiling materials creates incomplete combustion resulting in deposits which will tend to clog piston ring clearances. Another effect is ignition delays resulting in higher oil film stresses. Catalytic fines, originating from catalytic cracking processes can sometimes be found in heavy fuel oil and are an abrasive contaminant which can lead to engine breakdowns.
The damage resulting from bad quality fuel may well be difficult to attribute to the supplier of that fuel, because of the difficulty in proving when and where the fuel in question was taken on board. Prior to this invention it was not unusual to take samples of bunker fuel for analysis but such samples were usually taken only at the beginning and/or the end of the bunkering operation. It is possible for such samples to give a satisfactory analysis even though a substantial quantity of contaminants have in fact been included in the oil supplied, because the quality of that oil has varied during the course of the bunkering operation. For instance, water may be pumped on board during a relatively short part of the bunkering operation, perhaps as the supplier empties a tank.